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UC Cooperative Extension studies organic herbicides for weed control in landscapes

The safety of the weed killer glyphosate, the active ingredient in some well-known Roundup products, has been the subject of attention recently because of lawsuits that connected the chemical to cancer in humans.

Based on extensive scientific research, U.S. regulatory agencies have not banned glyphosate, but the publicity has increased interest in alternatives to the herbicide, which is the most widely used pesticide in the world. 

“Everybody is really clamoring for information,” said area integrated pest management advisor Karey Windbiel-Rojas. “Efficacy of organic herbicides is one of the most popular talks I am giving at the moment.”

Windbiel-Rojas and former UC Cooperative Extension environmental horticulture advisor Maggie Reiter launched research projects in 2019 to help fill knowledge gaps on the effectiveness of organic herbicides in urban landscapes – such as lawns, golf courses, parks, cemeteries and school grounds. (Reiter has since taken an extension educator position at the University of Minnesota.)

Professionals who manage landscapes like lawns, golf courses, parks, cemeteries and school grounds are searching for new ways to tackle weeds. (Photo: Pixabay)

Organic herbicides are pesticides made of compounds that occur in nature; and synthetic herbicides are compounds developed in laboratories. While both can be more toxic or less toxic to people and the environment, some people prefer using organic methods or chemicals.

On a small scale, a variety of organic solutions to weeds are readily available – such as hand pulling, hoeing and mulching. For larger jobs, professional landscape managers prefer applying an herbicide and look to UC Cooperative Extension scientists to know how well different options will work.

Reiter set up a study on at Ridge Creek Golf Course in Dinuba, and Windbiel-Rojas set up a study on a landscaped area with a mix of grasses and weeds in a parking lot at Sacramento State University.

In the Dinuba experiment, Reiter applied organic herbicides on 25-square-foot plots in four replications. The active ingredients of the organic herbicides included such naturally occurring chemicals as citric acid, clove oil, orange oil, acetic acid (vinegar four times stronger than that found in most home pantries), soaps, and caprylic acid, which comes from coconut and palm kernel oils.

The plots treated with citric acid and clove oil remained as green and lush as the grass in the control areas, which hadn't been treated at all. The areas sprayed with the other organic herbicides showed significant injury two days after treatment. However, 19 days post-treatment the plots treated with caprylic acid and herbicide soaps had completely recovered. The plots treated with orange oil and acetic acid recovered after 28 days.

Examples of herbicide efficacy for each herbicide treatment in Dinuba. (Photo: Maggie Reiter printed in CAPCA Adviser Magazine)

In the Sacramento State trial, Windbiel-Rojas used some of the same organic compounds, plus others with different natural ingredients, such cinnamon oil, pelargonic acid and ammonium nonanoate, which are drawn from fruit, vegetables and other plant sources.

Many products burned down both grasses and broad-leaf weeds after a few days, however, a couple weeks later, the weeds began to regrow or recover. In addition, some of the organic treatments are more acutely toxic to people than glyphosate.

“While organic, 20% acetic acid is very toxic to the person applying the herbicide,” Windbiel-Rojas said. “It will burn one's skin, hair and eyes so the applicator must wear more personal protective equipment than with some other herbicides. This material is also problematic to use in a public space because any bystanders could be exposed to drift during application.”

The research was published in the February 2020 issue of CAPCA Adviser Magazine. The findings of the research on organic herbicides for turfgrass are preliminary and UC IPM researchers will continue to investigate options.

Windbiel-Rojas will present “Glyphosate Alternatives and Organic Herbicides in Landscapes: Efficacy and Tradeoffs” at the Pesticide Applicators Professional Association Zoom webinar Dec. 2. View the agenda here: https://www.papaseminars.com/uploads/Seminars/11643.pdf. For more information and the registration link, visit https://www.papaseminars.com/seminars.  

Posted on Friday, November 20, 2020 at 8:34 AM
Focus Area Tags: Pest Management

UC ANR's new organic institute is swinging into action

The newly appointed Presidential Director for the Clif Bar Endowed Organic Agriculture Institute, Houston Wilson, has already initiated a needs assessment of organic agriculture in California, reported Lee Allen in Western Farm Press. Wilson is using surveys and focus groups to determine production needs within target commodities.

“Our mission will be to develop research and extension for organic production of things like tree fruits, tree nuts and raisins, commodities representing a significant portion of the entire Central Valley, but with very different cropping systems," Wilson said.

The diversity of California agriculture is represented in scale and systems - from orchards to vineyards to row crops and rice production.

"We're working on a cost-benefit analysis for commodities across the state to determine where gains can be had by developing better organic practices," Wilson said. "The argument about whether or not organic production can produce more yield is a hot topic. There are arguments that say organic can't yield as much as conventional and that may be because not that much has been invested in the organic effort compared to conventional agriculture. Metaphorically, it's like comparing a veteran player with a new kid on the team."

Price premiums for certified organic produce entice growers to convert to organic.

"Our job is to work with them, to identify and develop industry practices that make (organic production) move even more alluring," Wilson said.

A needs assessment for organic agriculture research and extension is underway.
Posted on Wednesday, June 10, 2020 at 8:44 AM
Focus Area Tags: Agriculture

Laura Burkle Seminar: Plant-Pollinator Interactions

Female leafcutting bee, Megachile fidelis, foraging on a Mexican sunflower. (Photo by Kathy Keatley Garvey)

One reason to research plants is that “they stay put.” But more about that later. Community ecologist Laura Burkle, associate professor...

Female leafcutting bee, Megachile fidelis, foraging on a Mexican sunflower. (Photo by Kathy Keatley Garvey)
Female leafcutting bee, Megachile fidelis, foraging on a Mexican sunflower. (Photo by Kathy Keatley Garvey)

Female leafcutting bee, Megachile fidelis, foraging on a Mexican sunflower. (Photo by Kathy Keatley Garvey)

Female sweat bee, Agapostemon texanus, on purple coneflower. (Photo by Kathy Keatley Garvey)
Female sweat bee, Agapostemon texanus, on purple coneflower. (Photo by Kathy Keatley Garvey)

Female sweat bee, Agapostemon texanus, on purple coneflower. (Photo by Kathy Keatley Garvey)

Posted on Tuesday, January 29, 2019 at 4:19 PM
Focus Area Tags: Agriculture, Environment, Natural Resources, Yard & Garden

Organic farmers and researchers strive to advance soil care

Organic farmer Phil Foster has developed a creative way to nurture the soil on his 200-acre farm near Hollister. He plants cover crops in a single line at the top of the planting bed, saving water and seed while keeping the furrows clear for irrigation.

"We were finding we couldn't use cover crops because of water," Foster said. The narrow strip makes the best use of the limited water supply, while garnering the benefits of cover crops - which buffer soil temperatures, inhibit weeds, increase soil microbial activity, improve water infiltration and add nutrients. Growing cover crops prepares the soil for the production of high-quality vegetables.

Organic farmer Phil Foster stands in front of a field with cover crops planted in strips at the top of the planting bed.

Foster is one of eight organic vegetable growers who are working with researchers at Chico State, Fresno State and UC Agriculture and Natural Resources on a project funded with a USDA grant designed to make significant improvements in soil care in organic production systems. He guided project participants around his farm, equipment yard and compost operation in early November to share the techniques he and his staff have developed over three decades to promote soil health.

Tiny pores and roots can be seen in the soil at the Foster farm.
 
UC Cooperative Extension farm advisor Sarah Light examines a soil sample. The agronomy expert, who serves Yuba, Sutter and Colusa counties, is a cooperator on the project.

Tour participants marveled at the soil characteristics, admiring tiny pores and roots in clods of dirt, evidence of the soil's capacity to move water and nutrients. They studied the plant and soil conditions after farm manager Efrain Contreras pulled a carefully crafted implement for rolling down the cover crop across the field with a tractor. 

Foster credited Contreras, a 30-year employee, for his role in building the soil on the farm. Labor, Foster said, is his biggest cost. He has 50 full time staff, many with 5 to 20 years of experience.

"They are the key to to the success of the ranch," Foster said.

Farm manager Efrain Contreras pulled an implement through a mature cover crop to show how the field can be prepared for planting.

Minimizing and, eventually eliminating, soil disturbance can be combined with organic groundcover, year-round root growth and robust biological activity in the soil to further promote soil health. Following the tour, the farmers talked about ways to attain the goal on their farms of no-till organic vegetable production. 

Foster said he will experiment with reducing soil disturbance to determine whether doing so will maintain or increase yields. Another farmer in the project, Scott Park of Meridian, Calif., 50 miles north of Sacramento, said he will dedicate eight acres of his organic farm to comparing the results when the cover crop is chopped and left on the soil surface to chopped and incorporated with tillage.

Paul Muller and Andrew Braitt of Fully Belly Farm in the Capay Valley suggested the researchers could help the farmers by identifying optimal, effective cover crop rolling techniques. Retired organic farmer Tom Willey of Madera suggested grant funds be used to purchase appropriate scale cover crop seeders for on-farm experimentation.

"We're making great progress," said project coordinator Jeff Mitchell, UC Cooperative Extension vegetable crops specialist. "By getting together regularly, we're seeing opportunities for moving further toward reduced-disturbance on the farms, identifying the equipment needs and establishing effective channels of communication."

Over the project's three-year term, the farmers and researchers will continue to experiment with soil-building techniques and share results.

Andrew Brait of Full Belly Farmers, foreground, looks at roots and nodulation of rhizobia on the cover crop. Kelly Mulville and Esther Park of Paicines Ranch are in the background.

 

A safflower and vetch cover crop growing in the autumn light.

 

Workers, in the background, manually weed the safflower and vetch cover crop.

   

Project coordinator Jeff Mitchell, UC Cooperative Extension vegetable crops specialist, and Phil Foster.
 
UCCE farm advisor Amber Vinches, center with sun glasses, is a cooperator on the project. Vinchesi serves vegetable crop farmers in Colusa, Sutter and Yuba counties.
Posted on Monday, November 26, 2018 at 8:35 AM
Tags: Amber Vinchesi (2), Jeff Mitchell (42), organic (26), Sarah Light (3), vegetables (22)
Focus Area Tags: Agriculture

University researchers and organic farmers to build soil as nature intended

A USDA grant will allow a group of California organic farmers to team up with researchers from the University of California, Chico State and Fresno State to determine whether tilling less soil on the farm will improve production of vegetable crops.

The aim is to duplicate the soil environment found in natural areas – typically concealed by plants, leaves and other organic debris – to improve agricultural soil health, increase production, reduce water use and avoid leaching nutrients out of the root zone.

“Tilling the soil is common on farms, but our research shows that it often isn't necessary, and can even be detrimental,” said Jeff Mitchell, UC Cooperative Extension agronomy specialist. “In nature, organic matter on the soil surface creates a protective layer and promotes biological activity that is beneficial to plants and the environment.”

A group of organic farmers, shown above, are working with UC researchers to minimize tillage and optimize soil characteristics on their farms.

The three-year project, funded with $380,000 from the USDA Natural Resources Conservation Service's Conservation Innovation Grant program, involves six organic farmers who are already experimenting on their own with cover crops, compost and minimum tillage to grow high-quality organic produce.

“This is a group of outstanding farmers,” Mitchell said. “It's very encouraging to see this sort of care for the soil. They recognize that taking care of the soil biology is useful to produce crops.”

One of the participants, Scott Park of Meridian, Calif., 50 miles north of Sacramento, has been building the soil on his farm for 38 years.

“We put 10 to 15 tons of biomass on every acre every year,” Park said. “This has given me good soil structure, water percolation and water retention, and we're having some really good results.”

Park said he tweaks his farming practices each year. To date, he has tinkered with reduced tillage, but isn't sold on a no-till system.

“I'm doing minimum till now, but it can be better,” Park said.

Teasing out those improvements is a goal of the project, which includes trials on four farms and two 12-acre demonstration plots, one at the UC West Side Research and Extension Center in Five Points and the other on the Chico State campus.

“Each of us will be trying to get closer to the goal of reducing tillage to promote soil health. We all want to develop strategies that might work, and not repeat mistakes,” Mitchell said.

The USDA grant funds will enable the farmers and researchers to gather accurate data about the agronomic and economic impacts of the new farming systems and use state-of-the-art equipment and technologies as they experiment with new techniques.

For example, the team is working with a Salinas company that is bringing a Spanish transplanting technology to California. The company, Tanimura & Antle Produce, will allow a demonstration of a plant tape that holds sprouts spaced ideally for a broccoli field planting in the West Side REC plot. (See video below or on YouTube at https://youtu.be/6pkmQVNjH1I .) The technology holds promise for reducing tillage, cutting back on labor, using less seed, and bringing the crop into production earlier in the season.

Planting cover crops is another way farmers and researchers will seek to improve soil health, though this process is a challenge in organic farming systems. On conventional no-till and minimum-till farms, the cover crop may be sprayed with an herbicide before planting seedlings in the cover crop residue. Possible solutions are chopping up the cover crop or using a roller-crimper machine.

“These technologies would provide considerable advantages in organic systems, but very little research has been done to quantify how these practices might influence soil function and cropping system resilience in California,” Mitchell said.  

As part of the project, a farmer network will be developed for information sharing, 18 public extension events will be held, six videos will be created and curriculum will be developed to extend the research outcomes.

For more information, contact Jeff Mitchell at jpmitchell@ucanr.edu, or (559) 303-9689.


 

In the video below, see an overview of transplanting technology developed in Spain that will be part of the soil building research.

Posted on Thursday, August 16, 2018 at 8:34 AM
Tags: CASI (15), Jeff Mitchell (42), organic (26)
Focus Area Tags: Agriculture, Environment

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